This invention relates to improvements in steering column assemblies, and to a support bracket for such assemblies.
Steering column assemblies for automotive vehicles and the like are increasingly required to be adjustable for rake and, in many cases, reach. This requires the column shroud, within which the steering column shaft attached to the steering wheel is rotatably located, to be fixed to the vehicle by a clamp mechanism which can be locked and unlocked to either prevent or permit adjustment of the column shroud position respectively.
One common arrangement uses a telescopic column shroud which comprises two tubes which slide one inside the other to permit reach adjustment. A fixing rail welded to one of the tubes is secured to a support bracket by the releasable clamp mechanism. Rake adjustment can be achieved by providing a support bracket which includes vertically extending slots through which the clamp mechanism passes. The clamp mechanism, which is secured to the fixing rail, can be moved vertically within these slots, taking the column with it to adjust rake.
A known arrangement for use in restricted spaces utilises a bracket in the form of an inverted U-shape having two arms depending from a base which have the vertical slots formed therein. The clamp mechanism includes a bolt which passes through the slots to link the arms together and the column is located between the arms. Tightening the bolt draws the arms together to squeeze them onto the column.
It is also known from WO2007/026224 to provide for a bracket in which one arm comprises inner and outer leaves. The outer leaf extends down from the bracket base as before, and the inner leaf is fixed to the free end of the outer leaf and extends back up towards the base. The clamp mechanism acts between the inner leaf and the other arm of the bracket. The function of the inner/outer leaves is to reduce variations in clamping force that arise during rake adjustment due to the clamp acting at different points along the clamp bracket arms. Both the inner and outer leaves can be made to flex such that changes in spring force of one leaf cancel out changes in the other as the clamp mechanism moves up and down.
In each case, the clamp mechanism typically comprises a cam that acts between a fixed part of a clamp pin and a part of one of the arms. The cam comprises a fixed cam part that is prevented from rotation by engagement of an anti-rotation feature in a slot in the arm and a rotating cam part that is typically secured to a locking lever. Rotating the lever causes the face of the moving cam to slide along the face of the fixed cam, varying the length of the cam in a direction along the axis of the clamp pin.
The anti-rotation feature is shaped so that it cannot rotate in the slot but is free to move along the slot. For instance, it may comprise a rectangular block that protrudes from the fixed cam part away from its cam face (or cam follower), the side walls of the block fitting snugly between the side walls of the slot. Any attempt to rotate the fixed cam part will be constrained by the slot.